The present invention relates to magnetic disks such as flexible magnetic disk units and rigid magnetic disk units.
The conventional magnetic disk unit comprises a spindle for supporting and rotating a magnetic disk, at least one magnetic disk, a magnetic head arranged in opposed relation to the surface of each magnetic disk for reading and writing signals and a positioner for holding and positioning the magnetic head, all the components being contained in a housing. A device of this type is disclosed in JP-A-62-197975.
Examination by the present inventors, however, shows that in the case where a disk having a diameter corresponding to a housing of predetermined size is driven in that housing, the reduction in the power required for disk rotation and the increase in seek velocity are limited.
The present invention has been developed in view of the aforementioned points, and the object thereof is to provide a magnetic disk unit which has a large capacity and a low power consumption as a whole.
In order to achieve the above-mentioned object, according to one aspect of the invention, there is provided a magnetic disk unit comprising a plurality of magnetic disks, a plurality of spindles for supporting and rotating the magnetic disks, a plurality of magnetic heads arranged face to face with the magnetic disk surfaces for reading and writing signals, at least one positioner for holding and positioning the magnetic heads, and a housing for accommodating the aforementioned component parts, wherein a plurality of the magnetic disks are arranged in the same plane without being overlapped in the housing of 11 mm or less in thickness.
According to another aspect of the invention, there is provided a magnetic disk unit comprising a housing which is, for example, for PCMCIA (Personal Computer memory-card International Association) Standard of PC card size: 54.0xc2x10.1xc3x9785.6xc2x10.1xc3x975.0 or less (Type II), 54.0xc2x10.1xc3x9785.6xc2x10.1xc3x973.3xc2x10.2 (Type I) (m/m), originally intended to accommodate a magnetic disk with a side having a predetermined data area, wherein a plurality of magnetic disks each smaller in diameter than the PCMCIA size""s magnetic disk are arranged in a plane within the housing, the magnetic disks having a total one-side data area equal to the one-side data area of the originally-intended magnetic disk.
According to still another aspect of the invention, there is provided a magnetic disk unit comprising at least two rotating mechanisms (spindles) in the housing and means for reading and writing information by selecting the rotating mechanisms.
The rotating mechanisms (spindles) are preferably arranged in a plane in the housing in order to achieve a thin structure of the disk unit. For example, a housing originally built for a 1.8-inch size disk is preferably adapted to accommodate two 1.3-inch magnetic disks, three 1.0-inch magnetic disks, or four 0.7-inch magnetic disks arranged in a plane.
Preferably, each positioner for holding and placing magnetic heads in position is separately configured in association with each magnetic disk spindle, or each positioner is shared by each one of groups of several magnetic disk spindles.
The outer dimensions of the housing for accommodating a plurality of magnetic disks in a plane may be not more than approximately 55 mm by not more than approximately 86 mm with a thickness of not more than approximately 5.0 mm or not more than approximately 55 mm by not more than approximately 86 mm with a thickness of not more than approximately 3.5 mm.
The thickness dimension of a magnetic disk is determined on the basis of various parameters:
(a) spindle thickness s+casing thickness ca
(b) disk thickness d+2xc3x97(head thickness (h))+casing thickness ca
(c) positioner thickness p+casing thickness ca, or
(d) circuit thickness ci+casing thickness ca.
The two dimensions s in the above paragraph (a) and p in paragraph (c) will be provide obstacles to make the disk thinner. The structural feature of a plurality of pairs of a spindle and a positioner will present a small driving power and a small dimension of thickness for the disk unit according to an aspect of the invention.
The magnetic disks are preferably arranged in the same plane as and without overlapping with circuit boards including a data writing and reading circuit board, a signal processing unit (circuit) board and a circuit board for controlling the starting operation of the magnetic disk spindles and the magnetic head positioners.
The above-mentioned effects are derived from the following operation. According to the present invention comprising at least two spindles arranged in a housing and selected for writing and reading information, even though a plurality of magnetic disks are arranged in the same plane in a housing for writing and reading information, individual spindles can be rotated with a low torque without reducing the information recording area on the disk since the disk associated with each spindle is very small in diameter. Further, power consumption can be reduced by rotating only a specified disk as required. The use of a magnetic disk smaller than the form factor size generally used permits the use of a thinner motor and a thinner spindle. The structure of the disk unit can thus be reduced in thickness.